/Engine/Source/Runtime/Engine/Public/Rendering/NaniteResources.h
Requests (or polls) an async operation that rebuilds the streaming bulk data from the cache. If a rebuild is already in progress, the call will just poll the pending operation. If true is returned, the operation is complete and it is safe to access the streaming data. If false is returned, the operation has not yet completed. The operation can fail, which is indicated by the value of bFailed.
bool RebuildBulkDataFromCacheAsync ( const [UObject](API\Runtime\CoreUObject\UObject\UObject) * Owner, bool & bFailed )